networking Basics

Networking -: A group of computers connected to gather with a via transmission media is called network We do network to share the  Files, Folder Printer and other Devices 

Types of Computer Networks

Networks are classified depending on the geographical area covered by the network

LAN

CAN

MAN

CAN

Local Area Network

A Group of computer connected to gather with in a small Geographical Area is called as LAN 

It Connects computers to share data and resources such as printer or faxes

Advantages of LAN:

Improves productivity due to faster work

Provides easy maintenance

New systems can be installed and configured easily

Disadvantages of LAN:

Limited number of systems can only be connected

Cannot cover large area

Network performance degrades as number of users exceeds

   

Campus Area Network (CAN)

Made up of multiple LAN's within limited area Connects different LAN's in a campus

Metropolitan Area Network

Interconnects networks within a city

Wide Area Network

Covers a wide geographical area which includes multiple computers

or LAN's e.g. Internet

  Open System Interconnection (OSI) Model 

 

OSI layer model define that how a message is transmitted between two points in the telecommunication network. There are seven layers of the OSI layers model and each layers plays different role in the network communications. The seven layers include the Application, Presentation, Session, Transport, Network, Data link and Physical layer. OSI layers model was developed by the ISO for the telecommunication standardizations. The seven layers divide the tasks of the data communication into the subtasks and complete the data transmission cycle. OSI (Open System Interconnectivity) model divides the complex network communication process. In the communication process, the control is passed from top layer to the bottom and from the bottom to the top layers.

Application Layer





Application layers support the applications such as file transfers, email, telnet, SNMP, DNS, Finger, BOOTP, MIME, SMB, network software and NETBIOS based applications. Application layer allow access to the services that support applications. It handles the flow control, error recovery and network access. Gateway works on the Application layer.
Presentation Layer

Presentation layer is responsible for the protocol conversion, data encryption, decryption and data compression. Presentation layer formats the data to be presented over the network. It also encodes and decodes the data. Gateway and redirectors work on the Presentation layer.
Session Layer

Session layer establish, maintain and manages the session between two computers. It is responsible for the name recognition so that only the designated parties can participate in the session. It manages that who can transmit the data at a certain time and for how long. NETBIOS, RPC and Mail Slots work on the session layer. Interactive login and file transfers are the examples of the session layers. It also reports the upper layer errors.
Transport Layer

Transport layer provides the transfer of data between the end systems and the host computers and it also controls the error recovery and the flow control. It provides reliable and sequential packet delivery. TCP, ARP, NETBIOS, SPX, ATP and UDP works at the Transport layer. Gateway, Brouter and cable tester works on the Transport layer. It provides the acknowledgement of the successful transmission and the requests the retransmission if some packets don’t arrive at the destination.
Network Layer

Network layer is responsible for the addressing, routing, determines the shortest possible path for the data packets and translates the logical network address and names to their physical address. The protocols such as IP, ARP, ICMP, IPX, OSI, DDP, IGMP, RIP and OSPF works on the network layer. Brouter, router, frame relay device, ATM switch and cable tester works on the network layer. Routing, forwarding, internetworking, error handling and the congestion control are the main functions of this layer.
Data Link Layer

Data link layer defines the procedures for operating the data links. It detects and corrects the packets transmit errors. It defines the formats of the data on the network. It is responsible for the error free transfer of the frames to the other computers via the physical layer. Data link layer is further divided into the Logical Link Control and the Media Access Control. The devices such as Bridge, Switch, ISDN router, NIC, Intelligent Hub and advanced cable tester works on the Data Link Layer. This layer is also responsible for the error checking, frame control and the synchronization.
Physical Layer

Physical layer defines the physical medium such as network cables, network cards, hardware and the physical aspects/mediums of the data transmission. The devices such as Repeater, Multiplexer, TDR, Amplifier and Hubs work on the Physical layer. It defines the techniques to transfer the data over the physical cables.
                   Network Topologies

Physical Topology means the physical design of a network including the devices, location and cable installation.
Logical Topology refers to the fact that how data actually transfers in a network as opposed to its design.
  Computer network topologies can be categorized in the following categories
• bus
• star
• ring
• mesh
• Tree.
Hybrid networks are the complex networks, which can be built of two or more above mentioned topologies

BUS TOPOLOGY
Bus topology uses a common backbone to connect all the network devices in a network in a linear shape. A single cable functions as the shared communication medium for all the devices attached with this cable with an interface connector. The device, which wants to communicate send the broadcast message to all the devices attached with the shared cable but only the intended recipient actually accepts and process that message.
Ethernet bus topologies are easy to install and don’t require muchcabling and only a main shared cable is used for network communication. 10Base-2 and 10BaseT are two popular types of the Ethernet cables used in the Bus topology. Also, Bus network works with very limited devices. Performance issues are likely to occur in the Bus topology if more than 12-15 computers are added in a Bus Network. Additionally, if the Backbone cable fails then all network becomes useless and no communication fails among all the computers. Unlike in the Star topology in which if one computer is detached from a network then there is not effect on the other computers in a network

Ring Topology

In ring Network, every computer or devices has two adjacent neighbors for communication. In a ring network, all the communication messages travel in the same directory whether clockwise or anti clockwise. Any damage of the cable of any cable or device can result in the breakdown of the whole network. Ring topology now has become almost obsolete.
FDDI, SONET or Token Ring Technology can be used to implement Ring Technology. Ring topologies can be found in office, school or small buildings

Star Topology

In the computer networking world the most commonly used topology in LAN is the star topology. Star topologies can be implemented in home, offices or even in a building. All the computers in the star topologies are connected to central devices like hub, switch or router. The functionality of all these devices is different. I have covered the detail of each networking devices in the separate portion of my website. Computers in a network are usually connected with the hub, switch or router with the Unshielded Twisted Pair (UTP) or Shielded Twisted Pair Cables.
As compared to the bus topology, a star network requires more devices & cables to complete anetwork. The failure of each node or cable in a star network, won’t take down the entire network
as compared to the Bus topology.

However if the central connecting devices such as hub, switch or router fails due to any reason,then ultimately all the network can come down or collapse.

Tree Topology

Tree topologies are comprised of the multiple star topologies on a bus. Tree topologies integrate multiple star topologies together onto a bus. Only the hub devices can connect directly with the tree bus and each Hub functions as a root of a tree of the network devices. This bus/star/hybrid combination supports future expandability of the computer networks, much better than a bus or star.

Mesh Topology

Mesh topology work on the concept of routes. In Mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. In the previous topologies star and bus, messages are usually broadcasted to every computer, especially in bus topology. Similarly in the Ring topology message can travel in only one direction i.e clockwise or anticlockwise. Internet employs the Mesh topology and the message finds its route for its destination. Router works in find the routes for the messages and in reaching them to their destinations.The topology in which every devices connects to every other device is called a full Mesh topology unlike in the partial mesh in which every device is indirectly connected to the other devices.

Summary

Topologies are the important part of the network design theory. A better network can be built if you have the knowledge of these topologies and if you know the difference between each topology

TRANSMISSION MEDIA 

Media a channel through which  we send and receive   the Data it may be wired or wire less 

  

Networking Cables are used to connect one network device to other or to connect two or more computers

Characteristics of Cables: Before buying any cable we should Check  

Segment Length – Length of single wire 
Attenuation – Indicates loss of signal 
Bandwidth – Amount of data carried by cable 
Number of Segments – Maximum number of segments in network 
Cost – Copper cables are cheapest, fiber optic cables are expensive

Types of cables used is computer Network 

Coaxial Cable 

Twisted Pair 

Fiber optic

Coaxial Cable

Coaxial cable is the kind of copper cable used by cable tv companies between the community antenna and user homes and businesses. Coaxial cable is sometimes used by telephone companies from their central office to the telephone poles near users. It is also widely installed for use in business and corporation Ethernet  and other types of  Local Area Networks

Coaxial cable is called "coaxial" because it includes one physical Channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can carry information for a great distance.

Coaxial cable was invented in 1929 and first used commercially in 1941. AT&T established its first cross-continental coaxial transmission system in 1940. Depending on the carrier technology used and other factors,Twisted Pair copper wire and Optical Fiber are alternatives to coaxial cable.

Types of Coaxial cable

RG 58

RG 8

RG 6

RG 59 

                                 RG 58 

Maximum segment length is 200 meters Interference protection is better than twisted pair cables  BNC-T connector is used to connect this cable  Used in thinnet (10BASE2)

network  Mostly used in  cctv 

                                        RG8

Maximum segment length is 500 meters,Interference protection is good compared to any copper cable,BNC-T  connector is used to connect this cable Used in 10BASE5 network  .

            RG6

Broadband quad-shielded cable that offers an,Provides lower attenuation characteristics,Useful in cable TV, CCTV and satellite dish antenna.

                                   RG59

Solid conductor is surrounded by a foam polyethylene dielectric,Useful in security camera, cable TV and home theatre 

Twisted Pair Cables 

Twisted pair cable consists of a pair of insulated wires twisted together. It is a cable type used in telecommunication for very long time. Cable twisting helps to reduce noise pickup from outside sources and crosstalk on multi-pair cables. this cables are 2 types UTP and STP

The most commonly used form of twisted pair is unshielded twisted pair (UTP)

Shielded Twisted Pair(STP) Cable is used to eliminate inductive and capacitive coupling.

Optical fiber cable

 A fiber-optic system is similar to the copper wire system that fiber-optics is replacing. The difference is that fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information.

FIBER OPTIC CABLE ADVANTAGES OVER COPPER:

• SPEED: Fiber optic networks operate at high speeds - up into the gigabits

• BANDWIDTH: large carrying capacity

• DISTANCE: Signals can be transmitted further without needing to be "refreshed" or strengthened.

• RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables.

• MAINTENANCE: Fiber optic cables costs much less to maintain.